1. Field of the Invention
This invention relates to an electronic parts-mounting apparatus which intermittently moves mounting heads having sucking nozzles each extending downward for being employed in sucking an electronic part and mounting the sucked electronic part on a circuit board.
2. Prior Art
Conventionally, an electronic parts-mounting apparatus of this kind has been proposed by Japanese Laid-Open Patent Publication (Kokai) No. 5-226884, which includes a main unit, a feeding section for feeding electronic parts to the main unit, and a mounting section for mounting the electronic parts on a circuit board, with the feeding section and the mounting section being arranged on opposite sides of the main unit in a fashion parallel to each other. The main unit includes a rotary table and twelve mounting heads arranged on an outer periphery of the rotary table at equally spaced intervals. Each of the mounting heads carries six sucking nozzles. The rotary table is intermittently rotated to thereby move the mounting heads between the feeding section and the mounting section in a rotational manner. During intermittent rotation of the rotary table, each sucking nozzle selected for operation picks up an electronic part by sucking and mounts the same on a circuit board at the mounting section.
Along a movement path of the sucking nozzles from a sucking station in the feeding section, at which electronic parts are sucked, to a mounting station in the mounting section, at which the sucked electronic parts are mounted on a circuit board, there are provided stations at which devices make access to the sucking nozzles e.g. for recognizing a position or orientation of a sucked electronic part based on a sensed image thereof, and for correcting the position or orientation of the same. Further, along the remaining movement path of the sucking, nozzles from the mounting station to the sucking station, there are provided other stations at which devices make access to the sucking nozzles e.g. for selecting one of sucking nozzles of each of the mounting head for operation, and for adjusting a level of the selected sucking nozzle. At a station immediately preceding the sucking station, the position of a selected sucking nozzle is corrected in a transverse direction, while a device is provided for detecting a degree of projection of the selected sucking nozzle and degrees of projection of the other nozzles.
The six sucking nozzles are carried by each mounting head in a manner extending downward therefrom and retracted upward therein. The six nozzles are removably provided so as to permit replacement thereof according to the kind of electronic parts to be mounted on the circuit board as desired. The replacement work is typically carried out at the mounting station.
According to the proposed electronic parts-mounting apparatus, however, sucking nozzles are replaced (removed and mounted) at the sucking station, whereas detection of a degree of projection of each nozzle is carried out at a station immediately preceding the sucking station. Therefore, if a sucking nozzle excessively projects downward due to a mounting error, there is a fear that the sucking nozzle projecting downward from the mounting head collides against a component part of the main unit, resulting in breakage of the sucking nozzle or the component part. Further, when the sucking nozzle progressively projects downward due to looseness of a screw for fixing the same, a check made at a single point along the circumference of the main unit i.e. at the station immediately preceding the sucking station cannot ensure timely detection of such a faulty sucking nozzle.